Precision Electroweak Studies of the Standard Model

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This 2-year bridge program will support the newly-hired PI (Deconinck) on three precision electroweak measurements of the Standard Model, our current best theory describing fundamental particles and their interactions. This bridge program will ensure research continuity in one ongoing SAP project (MOLLER) and in two future SAP projects (BL3 and EIC EW) while building a Canadian community. All three projects will transition to Subatomic Physics Envelope - Project support within 2 years: MOLLER onto the ongoing SAP project which will be due for renewal in 2021, and BL3 and EIC EW onto new projects. The comparison of parameters determined from precision measurements with theoretical predictions allow for precision tests of the Standard Model. This bridge program focuses on three approaches. 1) The PI and 1 PhD student will design, build, and test the pion detector system for the MOLLER experiment at Jefferson Lab, a precision measurement of the electron's weak charge. The MOLLER experiment will measure the parity-violating asymmetry in the scattering of longitudinally-polarized electrons from unpolarized electrons in a liquid hydrogen target. A background for the asymmetry measurement is photo-produced pions. We will add a lead absorber after the main MOLLER detectors to range out most of the electrons but letting through a large fraction of the pions. Behind this lead wall will be acrylic Cherenkov detectors read out by photo-multiplier tubes. One PhD student will design, build, and test the acrylic Cherenkov detector concept. 2) The PI and 1 PhD student will simulate and test the proton detectors for the BL3 precision neutron lifetime experiment at NIST. Since the 1990s there has been a persistent discrepancy between the neutron lifetime measurements using two experimental techniques: bottle and beam experiments. The BL3 experiment aims to improve the 2.1 s uncertainty of the past "beam" experiments to better than 0.3 s. To detect decay protons, the experiment will use a segmented silicon detector. One PhD student will simulate backscatter of protons on the segmented silicon detectors, and test their performance in our mass-spectrometer facility. 3) The PI and 1 shared postdoc will complete studies for electroweak precision measurements at the Electron-Ion Collider (EIC), using distributed simulation platforms already developed at JLab. One of the high profile efforts in nuclear physics is the EIC. This facility will allow for precise measurements of neutral-current electroweak observables. We have developed a distributed simulation workflow as part of the EIC software consortium, and thus well positioned to revisit generic simulations with new detector designs. With half of one postdoc, we will update studies of the electroweak mixing angle and form factor extractions based on the detector systems designed for the EIC. All three components ensure training of highly qualified personnel in areas relevant to the subatomic physics program.